Radioreceiving apparatus



q R. E. THOMPSON.

RADIORECEIVING APPARATUS. APPLICATION FILED AUG.21, 1911.

1,328,933, Patented Jan. 27, 1920.

62 fg ljg l IN! 'EX I'OR.

x circuit eXciting circuit.

new and useful Improvements 111 Radiois a specification.

" UNTiTED STATES ROY njrHoMPsoN,

PATENT OFFICE.

OFNEWYORK, N. Y.

namonnnrvme APPARATUS. I 1

To alt whom it may camera.

Be it known that 1, Roy E. THOMPSON,

a citizen of theUnited States, and a resident of New York city, county of New York, State of New York,'have-invented certain receiving Apparatus, of which the following Thisinventlomrelates to radio receiving apparatus.

Its objects, among others, are increased efficiency and simplicityof operation.

The invention consists of certain novel -constructional features of the. utilization which usually contains the detector, together with certain means forassociating saidcircuit with an exciting-circuit, as hereinafter described, all pursuant to discoveries made by me in extensive investigations of 'theradio receiving problem.

'The invention employs various features of circuit connections which are old in the radio art, and the useful novelty resides in the construction of the apparatus constructionwith the 'receiving antenna or Figure 1 1s a f nection which may be employed within the invention, 'as to which diagrammatically, there is nothing novel. t

Fig. 2 is avertical section-of a form of construction which .may be usedwithin the invention, of the. energy transformer, and particularly, of the secondary or detector coil when twocoils are used; and

Fig. 3, is a diagram, drawn in greater detail than that of Fig. 1, and containing at 40 the left an added feature whichmay be employed usefull in combination with the main feature 0 the'invention.

' r In Fig-1- the'antenna is 2, 6, 10 and'the detector circuit is 13, li, 16. The antenna 1 ,45 includes, tuning inductance 6 connected .to -earth 10 via an adjustable connection indie and connected air the top via 2' to any suitable aerial structure. Of the detector circuit or circuit ofutilization, 13 is the secondary coil,. 1e any suitable decated by arrow,

.tector and 16 the indicator or telephone,- the detector and telephone constituting the com plete indicating apparatus. 1 The word detector is employedxherein in its ordinarysense as belng a device which directly or indirectly serves to cause the receipt of diagram of a circuit con-' radio "frequency signals togcause the operaa telephone. 1 v

I have discovered thati-n the use of two circuits at a radio receiving station, closely vcoupled together, a transfer of energy from the first to the secondand its utilization in useful work in the second, can be effected equally well atany period of the first cirwit and wholly independently of the period Specification of Letters Patent. Pat nt 27,1920. Applicationfiled August 21,1917. Serial. nb.'1s7,347; v

tion of a: suitable indicating" device, such as Y of the second circuit, provided'that the sec- .ond circuit be constructed as described later. Heretofore at radio'receiving stations it has been customary to employ two circuits supplying the detector and telephone, these two circuits beingtermed the ,antenna ciredit and the secondary circuit, and heretofore' the most efficient ,use ofthe received energyfhas been obtained when both said -circuits were made resonant, and both adjusted to have the same or substantially the same time-period. The utility of this twotuned circuit arrangement 'was due to the facts that the secondaryycircuit not only received energy. from the antenna, but being a resonantcircuit, it permitted that energy to accumulate. to the maximum and thereby efliciently operate the indicating apparatus,

such as a detector and telephone, or in some cases, a telephone alone. This secondary circuit, also having the same time-period-as its primary circuit, thereby permitted the two circuits .to resonate harmoniously with consequent beneficial results, as is wellknown. L

This coupled-tuned circuit receiving ap- 'paratus (known. as "the Marconi type) proved so exceedingly useful in radio work that for many years it was not deemed possible to devise practical apparatus which 'was not of this type;

However, notwithstanding that this type was standard practice for many years, the art recognized that it" possessed certain seri- "ous disadvantages. Attempts were made to improve the type so as to eliminate these disadvantages, but the latter proved to be inherent in the type. The chef disadvantages were two first, the "inconvenience and delay involved in making fine adjustments in order to operate at best efliciency, and

second, the inefficiency of operation due to coupling difiiculties'incidental to the transfer ofenergy from the antenna to the secondary circuit. v

In my invention, all adjustments may be dispensed with save that of the antenna, and

in all of said coupling difiiculties are elimi-.

nated.

The first disadvantage in the coupledtuned circuit type was involved inthe ma-- the efficiency of the type, each time that a message at a different wave-length came in from a distant transmitter,

In fact, the highest efficiency of which this type was. ca-

pable could not be obtained unless theoper ator first by trial adjustments put the two circuits into the same tune. This usually involved first, an adjustment of the antenna circuit; then an adjustment of the secondary I circuit; then a re-adjustment of the antenna circuit; then a readjustment. of the secondary circuit, etc., sometimes including an adthe other hand,

, wasted, instead of transfer of ener I ary, likewise facilitated the re-transfer of en.

justment of two or circuit, so that, 'at'best, .it took a substantial length of time to put the apparatus into best condition. All this was a very serious disadvantage in practice, on account 'of the great importance of quick service. But this disadvantage was borne with, because it was of this type.

inseparable from the efficiency In my invention, there is equal efficiency with the coupled tuned-circuit type, without requirement of any adj ustmenfs of a secondarycircuit. V

The second disadvantage in the coupledtuned-circuit type'involved difficulties in the coupling between the two resonant circuits. If this c'ouplin' were too close,some of the energy accumu ating and persistentlyoscillating in the secondary, -was transferred back to the antenna,'a nd re-radiated and going forward to do useful work on theindicating apparatus,for the very fact that harmonious ersistent oscillation of the two, circuits facilltated the from primary to secondergy back from secondary to primary. On if the coupling, were then loosened in order to prevent such re-trans fer, then that resulted in a decrease of the efficiency of energy-transfer from theantenna to the secondary. .In practice a 'compromise was made by having the coupling neither very close nor very loose, i. e., not so close as to cause a re-transfer of considerable energy back to-the antenna, and not so loose as to prevent. the transfer of a substantial amount of energy from antennajto secondary This, however, did not remove, but merely .alleviated, the -d'ifliculty, and there yet remained a substantial loss of efficiency more elements in each from the antenna,

, apparatus.

I secondary coil of an oscillation transformer,

nant cumulative circuit, this condenserbe close enough to. transfer to the secondary all the energy supplied to the receiving antenna.

n my invention. there are no coupling difficulties because I eliminate entirely the accumulative action of the circuit supplied so that instead of a re- 3 transfer of energy' back to the antenna, the entire energy, transferred to the utilizati'on circuit, is instantly consumed therein in doing useful work in operatingtheindicating i In the best form of the coupled-tuned-cir cuit type, thesecondary' circuit included the and a condenser, in series with each other, and saaid condenser was in shunt or parallel between the detector and the secondary coil, the coil-and condenser constituting a reso-.

ing preferably variable to adjust the period 'of the secondary to "that of the antenna; or

ment has been provided vestigators have shown.

- portion as the fixed period of the else the inductance .in the secondary" was, var1able;-or both the condenser and 1nductance in the'secondary were varlable, in order to obtain the best tuning.

In other forms; of this coupled-tuned-ci'r cuit type,lin orderto reduce the manipulative operations of the receiving operator, such condenserhas been omitted, and then the secondary ,coil' was the only -a'djustable element in the secondary circuit. c (Of 3 course, in all cases, the antenna is adjusted; to be put in tune with the received waves,)-'

In yet other forms of this type, no adj ustj for-the secondary circuit, but it has beengiven a fixed period approximating the range of commercial fre-. quencies received on the antenna (no varia- I bility being provided for any reactancein i the secondary circuit), the idea having been 05 to eliminate all the troublesome' secondary adjustments, but yet to retain the advanta e of having the secondary more or less close orbroadly tuned tothe antenna. This form a 1 has been termed the non-adjustable or un- .110 tuned form, although the fact is that the secondary didhave a tune,. as various in- The difliculty with such attempted simplified form, however, was that the efficiency was reduced in prosecondaryf- 'was different from that of'received signals a to which theiantenna' was tuned. although such a modified receiving set of thecoupled-tuned-circuit type might be very ef-. ficient when the incoming waves had a J i That is,

period-which happened to be 'the same or because thecompromise coupling-was not nearly the same as the fixed period of the L secondary, yet'the efficiency for receiving .wavelengths higher or lower than the .period'of the secondary,.was

proportionately less, and the efficiency fell off rapidly for in-- creases of difference in periods of secondary a and received Waves. r

As tothe coupling troubles, constituting the second disadvantage of the coupledtuned-circuit type, no form of apparatus has been ,devised to-overcome this, prior to my invention. 9 v

-The invention herein is based upon the discovery, made by me, that the inefficiency of .said non-adjustable (so-called -untuned) secondaries wasdue to the presence of distributed capacity yet existing in the circuit, even in cases where no condenser (lumped capacity) was used in shunt to the detector and coil.. I

circuit cumulative to a substantialv degree. In other words, what I discovered was that when it was attempted to simplify the operation by omitting an adjustable condenser paralleling thedetector (in addition to the omission of adjustable inductance), such omission alone did not make the secondary circuit av non-resonant circuit, but. simply deprived it of the mechanical advantage, of being adjusted to have identically the same period as that to which the antenna was adjusted. It possessed thedisadvantages of a condition of resonance in'the secondary without the ability to take advantage thereof. It therefore was nothing else than an inferior form of "the coupled-tuned-circuit type, nothwithstanding that ,this modification has been termed as untuned secondary type by many writers simply because,

no adjustable condenser for exact tuning was provided in the secondary. The second- .ary was in fact tuned, although not ,to the exactitude required for the'highest efficiency vof the type.

In the practice of making secondary circuits without a condenser in parallel'to the detector and secondary coil, it has been assumed, apparently, that the omission of this condenser removed from the circuit all capacity which was acting to make it a tuned cumulative circuit. The fact apparently. has been overlooked that the circuit always possessed substantial capacity other than that "of the omitted condenser (especially that capacity which is resident in the secondary coil).

.1 have found that" the reason why the socalled untuned, i. e., non-adjustable sec-.

ondary, did not respond 'efficiently to the various wave-lengths,- was, the existence of such distributed capacity. This distributed capacity of the coil provided it with. ability to accumulate enough energy to be effective in re-actingon the driving circuit to such a degree as to make necessary the adjustment to the same period in order to eliminate such re-action' effect.

' I have demonstrated thatif the secondary {circuitl'be constructed to have so little capacity (in parallel to the detector and secondary coil) as to be substantially nonefiective-in making the secondary a tuned 'without anyreactance adjustments of the discovered that this distributed capacity was acting to make the circuit, then it is possible to operate a receiving statlon at maximum e fficlency for all possible perlods of transmitted waves,

vaperiodicity'oof the secondary, I have obtained in the following manner the same efficiency of reception at all present commercial Wave lengths, without any adjustment whatsoever of the secondary circuit.

The coupling between the antenna and the utilization circuit should be sufficiently close to eause an instantaneous and complete transferof energy from the antenna, and thereby-cause the creation of maximum potential in the utilization circuit, without any necessity for, (or any 'actuaL) substan- A tial accumulation of energy, pled-tuned circuit type; yet without any substantial loss of energy, and without any substantial re-transfer of energy back from the detector circuit to the antenna. This across the detector, and the resulting effect is passed directly, via the detector, to the telephone, or amplifier and telephone, or whatever constitutes the rest of the indicat-. ing apparatus. Under these circumstances, the utilizationcircuit being actually aperiodic, and no energy being accumulated therein, there is none of the coupling trouas in the couinstantaneous maximum potential is created 1 bl'es which existed in the coupled-tuned-circuit type, for there is no' re-transfer' of energy back from the utilization circuit to the antenna,

'stantaneously transferred from antenna to utilization circuit beingv instantly employed" in causing or controlling the indication of the signal. In all cases the non-adjustable utilization 'circuithas the same efficiency, a .115 All this; isparticularly true irrespective of the frequency of the trans mitted waves.

all the energy which was in;

when the natural period of the aperiodic} non-accumulative utilization circuit is farbelow 300 meters, (the latter being the shortzest .commercially used" wave length), andwhen the antenna is adjusted substantially above 300 meters (the lowest wave length r i now employed commercially) I In brief, the construction is such that substantially "all of the energy received on the antenna is iristantlypassed on to its place of utilization without any interval offaccumulation in the utilization circuit.

In usefully employing my discovery, I

reduce the capacity deleteriously efi'ective parallelbetween the detector and second- 'ary coil, in either or both of two -ways. First, .I. reduce, so far as practical or desirable, the distributed capacity of the coil itself, for in so far asthat is allowed to exist, it is effective in parallel to the coil and detector, and effective deleteriously as stated above. This reduction may be effected in any. well known way of constructing any ,coil to be without substantial distributed capacity. Second, 1.1mm the detector' in the circuit so that any capacity' which may exist anywhere in the circuit,

including any distributed capacity remaining in the coil, is in series with the detector and not'in parallel thereto. For example, I

locate the detector as near as practicable to an end of the secondary coil, as is indicated in Fig. 1,- where detector 14 is shown, in diagram, as being near the end of coil 13, and

'may be connected directlyto the end of the coil. This reduces the capacity of the lead this example 100 to 3600 meters.

' of p 3600 meters when connected to an average 40 For a receiver the antenna or primary which is to have a range of from 100 to ships antenna, the following dimensions are suitable to embody my invention.

Around, a. primary core 40 (Fig.2) of suit able insulating material, four inches in diameter and seven inches long, is Wound a" primary coil consisting of 280 turns of wire,

' llfyhaving a diameter over the insulation of approximately .05 inch. This primary winding is in two layers, and may be banked in acordance with the well-known method of winding coils for the elimination of layer capacity, in order to permit only a single frequency in the antenna for any given adjustment; but my invention otherwise is entirely operative without such banking. Suitable tape 42-4344, etc., may be taken'ofi, as desired, for purposes of ad- 1 justment of period of the antenna. Provided with means for slidin ameter, outside the insulation, of .05 inch,

all the way inside of the primary core 40 1s the secondary cylinder 45 which is 3% inches in diameter and 7 inches long. Around thiscylinder is wound a' single-layer secondary coil consisting of turns of conductor 46 of a dieach turn being separated from-each adsiderable length, or both. In different wave-length ranges) the total-numof coupling by.means of inductance.

jacent turn by .05 of an inch and .1 inch being left between centers of these turns. The conductor I have used for this is a cable consisting of 72 strands of N o. 38 wire, enameled and the entire cable being covered with the usual commercial silk insulation.

The extreme endsof the winding 46 are connected to binding posts 47 and 48 to which, in turn, are'connected the detector 14 and telephone 16 of Fig. 1;

The peculiarity of Fig. 2, which is typical of embodiments of my invention in coils for any range of wave-lengths, is that the utilization circuit has high inductance, without the capacity normallycorresponding thereto. The secondary coil is preferably of the same length as the primary coil (or the secondary is at least as long as-the primary) the two coils have as nearly as practicable the same diameter, and the secondary coil has suflicient inductance (at such length and diameter) to provide a coupling as close, in theory,as approximately 38%. Yet the capacity of the secondary coil is reduced, first,

by providing all the inductance in a single layer; second, by separating, the turns from each other; third, by limiting thetotal number of turns. Hence, in order to provide adequate inductance, the tendency is toward a secondary 'coil of large diameter, or conany case (of ber of turns is limited so as not to provide too great capacity. The single layer of winding is the second in importance of the above three items. If a less range than up to 3600-meters be used, the turns need not be separated-from each other, and also, if a still-shorter range be used, the winding need not be in a single layer. For a range upto 3600 meters the items specified for Fig. 2 are vastlypreferable, and for longer ranges are absolutely necessary. In any case, in order to obtain the desired close coupling, the two coils are preferably similar to each other in respect of their lengths and also of their diameters.

Although I prefer the two-coil type of coupling shown, yet an autotransformer or single-coil coupling maybe-employed with my invention, which is not concerned with the coupling save in the matters of sufficiently low deleterious capacity, and of sufficiently great inductance to permit full transfer of energy; The term inductance coupling is used herein to define any form case J'of an autotransformer coupling, the

"antenna-adjustment of'the single coil has no effect on the aperiodic circuit of utilization.

An object of my invention is the maximum efiiciency in respect of energy-transfer, with the minimum of manipulative adjustments. This object is substantially attained in the apparatus of Figs. 1 and 2, but is present in In the I an even higher degree in the apparatus of. Flg. 3, which includes the utilization circuit of Figs. 1 and 2 together with certain additions.

' In Fig. 3, 17 designates an antenna'corresponding'to the antenna 40f Fig. 1, which is connected to one terminal of the primary coil 18 "of a coupling transformer of such helical form that the secondary coil 19 may connected by be slidably inserted within coil 18 and withdrawn therefrom to place any desired portion of the whole length of said secondary coil 19 in a concentric position within said primary coil 18,so as to effect any desired degree of inductive relation therebetween.

The other terminal of the primary coil 18 and thejsuccessive turns thereof, are each leads (as 20, 21, 22) to switchcontactpoints (as 23, 24, 25) which are disposed in the path of aswitch-contact arm which may be swingingly moved to engagewith any desired one of said contact points 23, 24, 25, said arm 30 being connected by a conductor 31 to one terminal of a variable condenser 32, the other terminal of which is connected by. a conductor 33 with the earth 34:. e

Theturns of the secondary coil.,19 are disposedlinonly one layer at a distance apart,

coil 1-9 preferably is almost as great as the internal diameter of the primary coil 18, so.

to each other.

as in Fig. 2, and the external diameter of that these two coils arein close proximity One terminal of the secondary coil 19 of Fig. 3 is connected to one terminal of detector 37, the other terminal of which may be connected .to one side of a condenser 38, the other sideof'which is connected to the other terminal of the secondary coil 19. Connected with the opposite sides of the condenser 38 are the terminals of a head telephone receiver 39. f

The detector 37 as in Fig. 1, may be disposed in its circuit as nearas it is physically practicable to the secondary coil 19 so as to remove as much as possible of the capacity of'the secondary leads. The condenser 38 may be omitted, as in Fig. 1, to simplify the apparatus, since it is not essential for. a realization of the purpose of myinvention. It

may beused consistently with the invention, however, because it does not constitute a caacity efiective in parallel between the coupling coil and detector as would be the case of a condenser-connected across the terminals of'the .coil.

- The wires 50 and 51 connect to the antenna and ground 34respectively and are adapted to be connected'by the switch 50 and the.

leads 535 i with the high frequency oscillation-generator 55 which generator may be as shown (an oscillating audion of the wellknown type), or it may be any other form of generator for causing continuous oscillations continually lmpressed on the secondary coil rent through the telephones 19. This results in direct continuous current flowing through the telephones 39. If now waves of a slightly 'differentfrequency arrive from a distant sending'station, beats due to the difi'erence between the two "frequencies will be set up, and-the direct our- 39 will be caused to undulate at a. rate equal to the number of beats produced per second by the two frequencies, and these undulations will cause a movement of the telephone diaphragm resulting in sound of a pitch equal to the beats freguency.

he advantage of this arrangement is that by simply varying the period of the antenna, the beat-frequency is also varied;

and this, together with the novel utilization circuit of my invention, permits the maximum of efficiency to be obtained, with a minimum of adjustments or circuit variations. I v m I am aware of the fact that it is well known in the electrical art in general that distributed capacity in coils is undesirable.

-Many writers have mentioned the desirability of eliminating distributed capacity of coils wherever the coils are to be used, for the reason that a coil possessin' this distributed capacity will have local 51' set upin it. But I believe that I am the first to-dis'cover that a coil having no effective capacity, but at the same time, inductance sufficiently great to couple very closely to a second coil. will respond with- 105 The features. constituting a practical em- 115 bodiment of my invention are (1) a circuit of utilization lacking capacity efl'ective in causing accumulation of received ene rgy; (2) any suitable main receiving circuit or antenna capable of being tuned to trans- 120 mitted waves; (3) a sufiiciently close coupling of antenna and circuit of utilization to cause an instantaneous transfer of the energy from the antenna,

thereby creating a maximum potential in the circuit zation uwithout substantial accumulation therein; (.4) any suitable indicating apparatus capable of promptly consuming the transferred energy, thereby also reducing any tendency to persistence of the energy in equencies exactly to the second of utilii the circuit of utilizatioir and any tendency to re-transfer energy back to the antenna.

\In such apparatus, the transfer and utilization of energy is just as efiicient when the circuit of utilization isa thousand percent. out of syntony with the antenna as it is in a case of absolute syntony with the antenna.

The expressions hereinbut little capacity, substantially no capacity, and the like, mean that the capacity present, if any,

' is so slight that it does not prevent substantially maximum or equal efficiency at all wave-lengths over which-the antenna is designed to operate without any reactance ad justments of the utilization circuit. Hence the criterion of the presence of the invention, and of the amount of capacity corre-i: sponding to the invention, is such substan tially uniform efliciency of operatlon over tion circuit and notwithstanding its closev ness of coupling to the antenna, and thus is prevented any lmpairment of the most perfect freedom of oscillation of the antenna.

I claim: i 1. In radio receiving apparatus, the conibination withan antenna, of a circuit of antenna having a utilization, a primary coupling-coil in the v banked winding, and a secondary coupling-coil consisting ofa single layer of turns of conductor separated from each other,'said circuit of utilizatlon including said secondary coil and having substantially no capacity effective in parallel with said coil. 1

2. In radio receiving apparatus, the com:

bination with-an antenna, of a circuit of. indicating apparatus, without intermediary,

utilization, and a coupling-coil consisting of a single layer of turns of conductor separated -'from each other, saidfutilization circuit including said coil and having substantially no capacity efi'ectiv'e in accumulating received energy. v

3, In radio receiving apparatus, the combination with an antenna, of a circuit of utilization, and an inductance coupling, said utilization circuit having substantially no capacity effective in accumulating received energy,,but containing suflicient inductance to cause eflicien't transfer'of energy from the antenna to the place of utilization.

4. In radio receiving bination with a receiving antenna, of a circuit of utilization, and an inductance cou- Ipling, the part of said coupling in said utilization circuit being constructed to have substantially no'capacity'efl'ective in accn mulating recelvedenergy in said utilization apparatus, the con1-.

circuit; whereby uniform efliciency of redep tion is maintained over a range of various wave-lengths without adjustment of the period of the utilization circuit.

5. In radio rece ving apparatus, the comblnatlon wlth a recelving antenna, of. a circuit of utilization coupled thereto and con structed to have substaiitially no capacity effective in "accumulating therein, -whereby' uniform efficiency" of reception is maintained over a range of various wave-lengths without adjustment of received energy k time period of' the circuit of utilization.-,

6. 'In-radio receiving apparatus, the com binatlon with. a -rece1v1ng.antenna, of'a 011'- cuit of utlliz'ation,

an inductance coupling so i the part of which in said utilizationcircuit is constructed to haye substantially no capacity in parallel With the coil, and a detector connected by. a short lead to the cou capacity effective in parallel With the con pling inductance and detector.

8. In radioreceiving apparatus, the combination with-a receiving'antenna, of 'indi-,

cating apparatus, and a utilization circuit containing substantially no distributed capacity,and closely coupled to the antenna, whereby energy is transferred directlyfrom the antenna 7 to the indicating apparatus without intermediary accumulation.

9. In radio receiving apparatus, 'the combination with a; receiving antenna, of indicating apparatus, and a substantially noncumulative circuit of utilization adapted to eby the anbe closely coupled to the antenna, causing the transfer of energy from v tenna directly'to cause the-operation of the accumulation of energy in the circuit of utilization. v h

10; In radio receiving apparatus, the combination with a receivlng antenna, of variable frequency-determining element connect-.

nected to the coupling but having substan able frequency-determining element and sup plied by a local source of radio-frequency "ed therein; an inductance coupling includ-f F 1ng sald element, a c1rcu-1t of utilization conoscillations located at the receiving station 11. In radio receiving apparatus, the com- I bination with an antenna, of a utilization circuit, and an inductance couphng consisting of two coils of substantially equal length i in mutually inductive relation, the secondary coil comprlslng a single layer of turns of msulatedconductor, sa d insulated turns being separated from each other in spacei said antennalmay be tuned to Wave-length as utilization circuit including said secondary high as substantially above-three hundred coil and having substantially no capacity 1neters, 0f a non-cumulative utilization cir-- 10 effective in accumulating received energy. 7 cuit havinga fixed period of substantially 12. In radio receiving apparatus, the comless than three hundred meters. bination with an antenna provided with a frequency-determining element whereby the ROY E. THOMPSON. 

